1. Field of the Invention
This invention relates to a system for use in a machine tool for the automatic management or control of tool life.
2. Description of the Prior Art
Numerically or otherwise controlled machine tools having a system including a measuring unit have been proposed hitherto and put into practical use, in which such a system is used for automatically measuring the dimension of workpieces and correcting the tool offset of a cutting tool depending on wear on the cutting tool. However, the amount of tool feed position compensation includes the error component (radial deviation component of a spindle of a machine tool) due to mechanical deformation resulting from temperature rise of the machine tool, in addition to the component related to tool wear, and the proportion of the former component with respect to the latter component in the amount of tool offset or tool feed position compensation is too high to be negligible. Especially, in the starting stage of the cutting operation of the machine tool, the component related to tool wear is almost negligible compared with the error component, as defined above, due to mechanical deformation resulting from temperature rise of the machine tool, and in such a stage, this error component occupies almost the entirety of the amount of tool offset or tool feed position compensation. The prior art system has therefore been defective in that detection and accumulation of the net component related solely to tool wear is difficult, and thus, detection and control of tool life cannot be attained with desired high precision.